Fuel oil additive and method of making the same



United States Pat ent 3,523,767 FUEL OIL ADDITIVE AND METHOD OF MAKING THE SAME Andrew T. McCord, Snyder, N.Y., assignor, by mesne assignments, to Marrnanac Inc., Cleveland, Ohio, a corporation of Ohio No Drawing. Filed Mar. 29, 1965, Ser. No. 443,660

Int. Cl. C101 1/32 US. Cl. 44-51 10 Claims ABSTRACT OF THE DISCLOSURE This invention relates to fuel oil additives and more particularly relates to improvements in the physical properties of the additives and the methods of making the same to substantially reduce and prevent corrosion of the parts and the production of slag during the burning of residual fuel oils.

Heretofore, it has been known that residual fuel oils, also referred to as No. 5, No. 6 and Bunker C fuel oils, contain varying amounts of the elements, sodium, vanadium and sulphur in the form of compounds which are objectionable impurities in fuel oils. When the oil containing these compounds is burned, there are produced low melting slags comprising sodium salt, vanadic acids and sulphuric acids, such as sodium vanadates and sulphates. During the burning, sulphur dioxide is formed as a gaseous product of any sulphur which is not immediately converted to sodium sulphate. In the gas stream, i.e. the flue gases, sulphur dioxide and excess oxygen, catalyzed chiefly by vanadium oxides, combine to form sulphur trioxide. The sulphur trioxide combines with the steam in the flue gases to produce sulphuric acid which appears as a mist or liquid at the dew point. This frequently deposits on the heat exchange tubes, such as in the economizers and in the waste heat boiler tubes, and results in a serious corrosive condition.

The aforementioned flue gases generally contain nitrogen, oxygen, carbon dioxide, steam, sulphur dioxide and trioxide. The gases generally further contain dust comprised of metal oxides, compounds thereof, and at times varying amounts of carbon, hydrocarbons and carbon monoxide. When vanadium is present in the fuel oil some of the metal compounds are molten at relatively low temperatures and are corrosive to the metals.

X-ray diffraction studies have indicated in the dust, the presence of sodium vanadium vanadate (Na O "V 0 5V O which is a compound having a low melting point and which when molten is highly corrosive to metals. The V 0 in its structure is able to take up an oxygen atom and transfer the same to the metal, thereby causing the metal to oxidize. The vanadate, now short an oxygen 3,523,767 Patented Aug. 11., 1970 Fee atom, takes this from the flue gases and so the metal oxidation cycle (corrosion) is continued.

When fuel oils which contain appreciable contaminant compounds, such as vanadium and sodium, are burned in high temperature tube boilers, some slag is deposited on the tube surfaces, particularly on the super heater tube surfaces. This results in a heat barrier and in order to maintain the rate of heat transfer, or in other words, to maintain a steady rate of steam or power production, more fuel must be burned to increase the combustion temperature in order to force the heat through the slag barrier. This condition results in an ineflicient and as a consequence, more expensive boiler operation.

Heretofore, it has been well known that magnesium oxide, introduced into the flame or burner, will to some extent combat the deleterious effect of sodium and vanadium contaminants, but it is also well known that this method is not completely satisfactory; it is diflicult, complicated, inefiicient, and usually causes excessive abrasion of equipment. In some cases, magnesium sulphate solutions have been mixed with the fuel just before the oil is burned. This is not particularly easy to accomplish and is also inefficient. Many attempts have been made to mix magnesium oxide or hydroxide with fuel oil, but in these cases severe erosion and abrasion in the pumps and burner nozzles resulted because of the abrasiveness of the oxide particles. It has also been found that while oil soluble magnesium compounds, such as magnesium naphthenate, are excellent materials for reducing the corrosion and slagging because of vanadium and sodium contamination they are too expensive for effective application.

Moreover, it has been found that in addition to being efficient and economical, an additive must meet other requirements or tests. Accordingly, such additive must be non-abrasive, should not damage or impair operation of the equipment and should not interfere with the normal operation thereof. Furthermore, the additive must be susceptible to usage with a minimum of time and eflort. In accordance with the present invention, all of these factors have been taken into consideration. Hence, though magnesium hydrate slurries may be emulsified in fuels they generally have no useful application. These emulsions are in the form of thick creams which do not pump or transfer easily and which are unstable. They quickly and easily break into an oil phase and a water phase. Mixtures of dry magnesium or aluminum hydrates in oil are, at best, poorly dispersed, highly abrasive, and tend to rapidly settle out when blended with fuel oils. Heretofore better results have been obtained by blending magnesium hydrates in water slurry with diluent oils containing some dispersing agents. Such types of blend eventually break leaving the metal hydrate in the oil phase. In such blend, however, considerable free water is also retained-emulsified by the dispersing agentso that the material produced is a thick cream when the total solids content approaches 40% to 60%. Attempts to pump this type of material in the metal pumps has resulted in intense abrasion and rapid wear to the parts. It is also known that magnesium alone does not produce the highly refractory compounds which can be produced by mixtures of magnesium and aluminum compounds.

Accordingly, an object of the present invention is to provide an improved fuel oil additive which will substantially retard or eliminate the corrosive and slagging effects of vanadium and other such contaminants present during the burning of residual fuel oils.

An object of the present invention is to provide a fuel oil additive of the character described having improved low viscosity and dispersion characteristics, which is nonabrasive, and which may be easily and quickly mixed with the fuel and without settling therefrom.

Another object of the present invention is to provide a fuel oil additive of the character described having improved pump-ability and which can be blended efliciently with the fuel oil without in any way diminishing its pumpability properties.

A'further object of the present invention is to provide a fuel oil additive of the character described which before being added to the fuel oil has improved stability and pumpability characteristics, which has viscosities not exexoeeding 2000 centipoise when the useful solids concentration is 60% or more, and which because of the complete and uniform orientation of an organic layer on the particles is non-abrasive when burned with the fuel oil.

Another object of the present invention is to provide a fuel oil additive of the character described which will, when burned in combination with residual fuel oils, produce a dry powdery ash that will not fuse even at temperatures up to 2800 F.

A further object of the present invention is to provide a fuel oil additive of the character described which upon burning with the residual fuels will keep the tube surfaces clean and so substantially increase the heat transfer, economy and efficiency of the installation, and which will decrease the clean-out and down-time during its operation.

Another object of the present invention is to provide a fuel oil additive of the character described which upon burning with the fuel oil will react with the condensation products on the tubes and other parts to prevent corrosion thereof and in a manner which is more eflicient and economical than heretofore known methods.

Another object of the present invention is to provide a fuel oil additive of the character described which, when burned with residual fuel oil, will retard or prevent the formation of smoke and unburned carbon deposits.

A still further object of the present invention is to provide a method of producing magnesium hydrate in situ in the fuel.

Still another object of the present invention is to pro vide a method of stably suspending a finely divided, oilinsoluble metallic additive, such as aluminum, chromium, copper, manganese, or zinc hydrate, by magnesium hydrate dispersed in oil.

Other objects of the present invention will be apparent from the following description and claims, which, by way of illustration, show a preferred embodiment of the invention, and the principles thereof, and what is now considered to be the most advantageous mode in which to apply such principles. Other embodiments embodying the same or equivalent principles may be applied by those skilled in the art without departing from the scope of the present invention.

In brief, the present invention is directed to a fuel oil additive and method of making the same which comprises suspending highly stable dispersions of non-abrasive compounds, such as the hydrates of aluminum, chromium, copper, manganese or zinc, in an organic solvent by magnesium hydrate dispersed in oil; which additive incorporates a maximum reactive solids concentration and a minimum viscosity to produce a thin, smooth liquid that is readily pumpable at room temperature. Generally, the additive may be made by reacting an aqueous slurry of magnesium hydrate with an organic solvent containing an ammonium or amine soap in an amount sufficient for substantially complete and uniform orientation with the surface molecules of the hydroxide particles to produce magnesium hydrate in situ in the solvent; blending' the hydrate in solvent with at least one non-abrasive compound, such asthe hydrates of aluminum, chromium,

4 copper, manganese or zinc, in an amount sufficient to provide a thin, smooth pumpable liquidhaving a-solids-content, calculated as hydroxide, in the range between about 56% to 61%, by weight, and a viscosity not exceeding about 2000 centipoise, as determined herein.

The residual type fuel oils to which the present invention is directed and which need my additive are principally characterized as No. 5, 6 and Bunker C fuel oils. corresponding to those specified by the NBS Commercial Standard Specifications for Fuel Oils CS12-48. The No. 5 fuel oil is generally a distillate fuel containing major amounts of residual materials. The No. 6 fuel is the heaviest grade and consists principally of residual materials. These residual type fuels are produced from petroleum by methods known in the art.

Though it is not intended to be restricted by any theory as to the reactions occuring herein, it has been found that magnesium hydrates formed in situ in the oil can best be achieved by reacting only and all the surface molecules of magnesium hydroxide with the ammonium soap of long chain fatty acids. Accordingly, by consideratiton of the crystal structure and mathematical treatment, it has been determined that in 1.0 micron crystals of magnesium oxide, only about 0.126% of all the molecules are in the surface, and in 0.1 micron crystals, only about 1.26% of all the molecules are in the surface. Similarly, in the case of magnesium hydroxide, it can be shown that in 1.0 micron crystals, only about 0.1% to 0.2% of all the molecules are in the surface and in 0.1 micron crystals, only about 1% to 2% of all the molcules are in the surface. It is believed that the fatty acid chains orient themselves away from the surface of the hydroxide particles and so lend to the particles the properties of small crystals of hydro carbons which behave like crystallites of paraffin wax. This is believed to be the case because when the solvent solution of the ammonium soap of long chain fatty acids, in amounts corresponding to that which would react with only the surface atoms of the crystallites, is mixed with a magnesium hydrate slurry, ammonia is evolved and substantially all of the magnesium hydrate appears in the oil phase. Moreover, it has been demonstrated that when a stoichimetric amount of fatty acid (two fatty acid molecules being required to react with the two hydroxyls of the Mg(OH) molecules) was reacted with magnesium hydroxide, the reaction was extremely violent and rapid. The fatty acid did not stop at the surface of the particles, but continued to react with the entire particle, thereby producing a magnesium soap. This was a thick oil-like material which eventually became crystalline. Conversely, if only a small amount of the fatty acid was reacted with a large quantity of magnesium hydroxide, much of the fatty acid did not even come into contact with the particles, while a minor amount reacted completely with the particles. Pure magnesium soaps are soluble in organic solvents but quickly become gels.

In accordance with the present invention, it has been found that the fatty acid can most effectively be reacted with only the surface of the magnesium hydroxide particles by first dissolving the fatty acid in a hydrocarbon solvent, neutralizing the mixture to produce in solution or in dispersion a soap of the fatty acid, and then blending the mixture of soap in the solvent with a slurry of magnesium hydrate. The reaction may be demonstrated by dissolving about 4% of a fatty acid, based on the weight of magnesium oxide (MgO), in a solvent such-as No. 2 or No. 3 fuel oil, kerosene, petroleum, gasoline, lubricating oil or other such petroleum fraction. The mixture may then be neutralized, such as by the addition of ammonia or an amine, to produce an oil-soluble, ammonium or amine soap of the fatty acid dissolved in the solvent. To the solution of soap in the solvent, may then be added magnesium hydrate in a slurry form. The particle size of the magnesium hydrate was in the range of between about 0.1 to microns with most of the particles being in the range between about 0.2 and 0.5 micron, thereby requiring about 4% of the fatty acid to react with substantially all of the molecules on the surface of the particles. Upon stirring of the mixture, ammonia was liberated and a thick emulsion at first resulted which rapidly broke into a water phase and an oil phase. The oil phase appears as a smooth, oily cream of magnesium hydrate particles coated with the fatty acid which assays a solids content of approximately 40%, calculated as MgO, and 60%, calculated as Mg(OH) by weight. Hence, from such reaction it is believed that the ammonium soap of the fatty acid must react with only the surface of the magnesium hydroxide particles and with the ammonia being freely liberated during the reaction on the particle surfaces.

The oil-soluble fatty acid radicals suitable for use in the present invention may include any long chain fatty acid, such as those containing 6 carbon atoms or more. The acid may be saturated or unsaturated though the saturated acids are generally preferred. Tall oil acids and heads are particularly suitable. Branched chain carboxylic acids, diand tri-carboxylic and the like are also useful in accordance with the invention.

A magnesium hydrate formed in situ in the oil is further illustrated by the following examples:

EXAMPLE 1 In a mixing device, there was placed approximately 140 pounds of magnesium hydroxide aqueous slurry and containing approximately 88 pounds of magnesium hydroxide (equivalent to 58 pounds of magnesium oxide). The volume of the slurry was calculated to be approximately 11.47 gallons.

In another container, approximately 4.3 pounds of a distilled fatty acid was dissolved in No. 2 fuel oil and the volume diluted to approximately 5.75 gallons using the No. 2 fuel oil as the diluent. A 30% aqueous ammonia was then stirred slowly into the solution until a pH of approximately 8 was attained. It was observed that 0.80 pound of the aqueous ammonia was used and also observed that the resulting solution of soap had a faint odor of ammonia. This solution was then added slowly to the aforementioned 140 pounds of magnesium hydrate with continuous mixing for about 45 minutes. After all the solution had been added, the mixture slowly thickened and then separated into two phases: a stiff oily paste and clear water. It was noted that the pH was above 8 and the odor of ammonia very strong during the mixing.

The weight and volume balance of this method is shown as follows:

In the foregoing-example, it was determined that approximately 1243 pounds of the oil phase having a volume of approximately 10.465 gallons resulted. This oil phase contained the equivalent of approximately 58 pounds of magnesium oxide. It was observed that since the original 140 pounds of magnesium hydrate slurry contained approximately 56 pounds of free water and approximately 84 pounds of magnesium hydrate by calculation and since 56 pounds of water was actually removed in the method, the reaction removed substantially all the free water in the original slurry.

Moreover, it was determined that the resulting oil phase Weighed approximately 11.87 lbs./ gal. and contained approximately 5.54 pounds of magnesium oxide in the form of 8.04 pounds of magnesium hydrate. This oil phase was then diluted with No. 2 fuel oil to weigh approximately mately 42%, by weight, of contained magnesium oxide (MgO) or 61% of magnesium hydrate. The viscosity of this final oil phase was determined to be approximately 1500 centipoise, as determined by the modified Brookfield viscosimeter, No. 4 spindle, 20 rpm. at F. The formulation of the final oil phase thus prepared was as follows:

Ingredients: Percent weight Magnesium oxide 42 Combined Water 19 Residual fuel oil 39' Magnesium hydroxide 61 Residual fuel oil 39 EXAMPLE 2 Example 1 was repeated, except that the fatty acid was not neutralized with ammonia. In this method, the mixing of the fatty acid in oil with the magnesium hydrate slurry was somewhat shorter and the mixture separated into two phases with only about 35.7 pounds equivalent to 4.3 gallons of water separating from the system. Compared with the method in the preceding example, at least 20 pounds of water must have remained in the oil phase. This final oil phase weighed approximately 11.2 lbs./gal., and exhibited a viscosity of approximately 6800 centipoise, as determined herein.

Under the same test condition as Example 1, the increased viscosity was attributed to the residual water, poor distribution and orientation of the fatty acid on the particle surfaces. The weight and volume balance of this method is shown as follows:

In this example, it was determined that approximately 144.8 pounds of the oil phase having a volume of approximately 12.92 gallons resulted. This oil phase contained the equivalent of approximately 4.49 lbs/gal. of magnesium oxide (MgO) or 6.49 lbs./ gal. of magnesium hydroxide Mg(OH) From the foregoing examples, it is apparent that the use of a fatty acid soap produced an oil phase containing more magnesium hydroxide (Mg(OH) per gallon and with an exceptionally low viscosity as compared to the same product made by the use of only a fatty acid.

In accordance with the present invention and subsequent to the preparation of the magnesium hydrate disposed in situ in the oil, as described above, a finely divided, non-abrasive compound may be added to the oil phase. To most effectively retard the slagging effect of vanadium and other contaminants, it is preferred to use compounds of aluminum, such as the hydrates of aluminum. Most effective of the hydrates is a pigment (Al A -3H O) having a particle size of about 1 micron, and bauxite (Al O -2H O) having a particle size in the range between about 0.1 to 10 microns. These hydrates of aluminum are then blended with the oil phase described in Example 1 to produce a thin, smooth, pumpable slurry having a viscosity which is not substantially greater than that of the magnesium hydrate oil phase.

The aluminum hydrates may be blended with the oil phase in an amount sufficient to give the desired concentration of magnesium and aluminum in the additive. In the present invention the oil phase of Example 1 can be blended with the aluminum hydrates to produce any ratio of magnesium to aluminum (MgrAl). The most effective blends of magnesium and aluminum, calculated as oxides, have been found to be in the range from about 1:0 to 10:1. Preferably, the weight ratio is about 1:1

The total content of the solids may vary depending upon the particular application of the additive. It has been found most desirable, however, to introduce into a gallon of oil the highest possible concentration of solids without increasing the viscosity beyond the point where the mixture becomes difiicult to pump. It has been found that the total solids content of the additive is in the range from about 56 %to 61%. Preferably, the total solids content is 61% by weight. Larger concentrations may be employed containing up to 87%, by weight, when it is desired to store the additive for extended periods of time. In such cases it is ordinarily necessary to mix and blend the additive with a solvent prior to use.

Typical additive blends are further illustrated by the following examples:

EXAMPLE 3 Magnesium hydrate in situ in the oil was prepared as described in Example 1.

In another container, approximately 4 pounds of a long chain fatty acid was dissolved in No. 2 fuel oil and diluted to approximately 8 gallons. To this was added approximately 100 pounds of a pigment grade of aluminum hydrate (Al O -3H O). The volume of this batch was approximately 13.5 gallons. This batch was then diluted to 14.55 gallons with No. 2 fuel oil to facilitate handling.

The aluminum hydrate batch was then blended with approximately 124.30 pounds or the equivalent of 10.465 gallons of magnesium hydrate in situ (Example 1). The additive blend was then diluted with approximately 14.00 pounds or the equivalent of 2.00 gallons of No. 2 fuel oil. The additive blend was then finally adjusted by the addition of approximately 2.695 pounds or the equivalent of 0.385 gallon of No. 2 fuel oil.

The total solids content of the additive blend was approximately 58 pounds of magnesium oxide and 65.4 pounds of aluminum oxide equivalent to 4.5 lbs/gal. The additive blend was found to contain 2.115 lbs./ gal. of magnesium oxide and 2.385 lbs./ gal. of aluminum oxide. This was calculated as 1.27 lbs./ gal. of magnesium and 1.27 lbs. /gal. of aluminum or a weight ratio of 1:1.

The volume and weight balance of the additive blend is shown as follows:

The formulation and properties of the additive blend are as follows.

Ingredients: Percent weight Magnesium oxide 18.90 Aluminum oxide 21.30 Combined water 20.25 Residual fuel oil 39.55

Magnesium hydroxide 27.90 Aluminum hydroxide 32.55

Residual fuel oil 39.55

Properties:

7 Appearance Ihin pumpable slurry. Wt. ratio (Mg/Al) 1:1. Sp. gr. at'68 F. 1.35. Particle size rnieronsf; 0.5-10 Flash point (PM) 150 F. v Viscosity F. Brookfield No. 4 spindle: V C.p.s. 20 r.p.m. 1700 10 r.p.m. e 3300 Brookfield No. 6 spindle: I

20 r.p.m 2200 10 r.p.m. 38.00

EXAMPLE 4 In another additive blend the ratio of magnesium to aluminum (Mg/Al) was adjusted to 1021 by the addition of only the necessary amount of aluminum hydroxidein oil to the magnesium hydrate batch described in Example 1. This illustrates that the magnesium hydrate in Example 1 can be blended with varying amounts of the aluminum hydrate batch in Example 3 to produce any desired ratio of (Mg/Al) for a particular application.

The properties of the additive blend are as follows:

Wt. ratio (Mg/A1) 10:1 Sp. gr. at 68 F. 1.305 Particle size microns 0.1-1.05 Flash point (PM) F 147 Fire point (COC) F 215 Pour point F 5 Viscosity F 80 Brookfield No. 4 spindle: C.p.s.

20 r.p.m. 167 10 r.p.m. 2900 Brookfield No. 6 spindle:

20 r.p.m. 2180 10 r.p.m. 4000 In accordance with the present invention, other nonabrasive compounds may be adde to the magnesium hydrate oil phase. To effective retard or prevent the formation of smoke and/or unburned carbon during burning of the residual fuel oil, it is preferred to use minor amounts of at least one non-abrasive compound, such as the hydrates of chromium, copper, manganese or zinc. Such compounds, when added, are preferably present in the range between about trace to about 6%, by weight, with the preferred amount being about 2% by weight.

These compounds may be added to the magnesium hydrate oil phase along with the aforementioned aluminum compounds, such as-aluminum hydrate, in a weight ratio of between about 1:0 to 1:1 so as to provide a solids content, calculated as oxides, in the additive of between about 56% to 61%, by weight, as-aforesaid.

EXAMPLE 5 Magnesium hydrate in situ in the oil was prepared as described in Example 1 and blended as in Example 3, except that approximately 94 pounds of aluminum hydrate (Al O -3H O) was mixed with approximately 6 pounds of chromium hydrate (Cr O -3H O) to replace the pounds of the aluminum hydrate in Example 3. The formulation and viscosity of the additive blend are as follows. 5.

Ingredients: Percent weight Magnesium hydroxide 27.90 Aluminum hydroxide 29.05 Chromium hydroxide 3.50 Residualfuel oil Q 39.55

Brookfield at 80 F., No. 4 spindle: C.p.s. 20 r.p.m. f 1070 10 r.p.m. 170O 9 Brookfield at 80 F., No. 6 spindle:

20 r.p.m. 1200 10 r.p.m. 2000 From the foregoing description and examples, it will be apparent that the present invention provides a method and composition for making an additive which will substantially retard or eliminate the corrosive and slagging effects of vanadium and similar contaminants during the burning of residual type fuels. In the present invention there is produced an improved additive composition which upon burning in the fuel provides a dry ash that will not fuse even at temperatures up to 2800 F., thereby materially increasing the economy and efficiency of the operation.

I claim:

1. An oil soluble fuel oil additive characterized by improved stability and pumpability for use in reducing the corrosive effects of contaminants present in residual type fuel oils during the burning thereof, said additive made from the steps comprising, providing an aqueous phase comprising an aqueous slurry of magnesium hydrate containing finely divided, oil insoluble magnesium hydroxide particles, dissolving a long chain fatty acid containing at least six (6) carbon atoms in a hydrocarbon oil solvent and in an amount sufficient to react substantially only with the surfaces of said particles, adding to the acid in solvent mixture a neutralizer selected from the group consisting of ammonia and amine to produce in the solvent an oil soluble soap of said fatty acid, blending together the mixture of soap in said solvent and said magnesium hydrate slurry to react said soap substantially only with the said surfaces of said particles to form a generally hydrocarbon coating on said particles thereby to enable said particles to separatesubstantially free of waterfrom said slurry and into said solvent, and then separating the particles in the solvent from said aqueous phase to produce magnesium hydrate, in situ, in said solvent to give said additive for use with said residual type fuels.

2. An additive made in accordance with the method of claim 1, wherein the solids content of the magnesium hydrate, calculated as magnesium oxide, is at least 38% by weight, and wherein the viscosity of the hydrate insolvent does not exceed 2000 centipoise, as measured on a modified Brookfield viscosimeter at 80 F.

3. An additive made in accordance with the method of claim 1, comprising adding to the magnesium hydrate insolvent at least one non-abrasive compound selected from the group consisting of the hydrates of chromium, copper, manganese and zinc, in an amount sufficient to retard the formation of smoke and unburned carbon deposits upon the burning of the oil.

4. An additive made in accordance with the method of claim 3, wherein the solids content of said slurry, calculated as oxides, is in the range between about 56% to 61%, by weight, and wherein the weight of ratio of said magnesium hydrate to one of said non-abrasive compounds is about 1:0 to 1:1.

5. An additive made in accordance with the method of claim 1, wherein aluminum hydrate is added to said magnesuim hydrate in situ in said solvent.

6. An additive made in accordance with the method of claim 5, wherein at least one non-abrasive compound selected from the group consisting of the hydrates of chromium, copper, manganese and zinc is added to said magnesium hydrate in situ in said solvent.

7. An additive made in accordance with the method of claim 1, wherein at least one of said non-abrasive compounds is present in said additive in an amount in a range between about trace to about 6%, by weight.

8. An additive made in accordance with the method of claim 1, wherein at least one of said non-abrasive compounds is present in said additive in an amount of about 2%, by weight.

9. An additive made in accordance with the method of claim 5, wherein the solids content of said magnesium and aluminum hydrates, calculated as oxides, is in a range between about 56% to 61% by weight, and wherein the magnesium and aluminum are present in the weight ratio of between about 1:0 to 10: 1.

10. An additive made in accordance with the method of claim 5, wherein the magnesium and aluminum hydrates, calculated as magnesium and aluminum, are present in the ratio from about 1:0 to 1:1 by weight, and wherein the composition has a viscosity on a modified Brookfield viscosimeter not exceeding 2000 centipoise at F. to provide a thin, smooth slurry which is pumpable at room temperature.

References Cited UNITED STATES PATENTS 2,487,334 11/1949 Hansley 252390 2,671,758 3/ 1954 Vinograd et al. 445 1 3,067,018 12/ 1962 Voorhees 44-51 3,111,381 11/1963 Panzer et a1 4451 FOREIGN PATENTS 200,149 11/ 1955 Australia.

DANIEL E. WYMAN, Primary Examiner Y. H. SMITH, Assistant Examiner US. Cl. X.R. 4460, 66, 68 

